This is a revised application for the Statistics Epidemiology. and Data Management (SED) Core. The SED Core will advance HIV research and improve the quality of applications submitted by HIV Center-affiliated researchers by providing advice and assistance with state-of-the-art statistics, epidemiology, and data management. The Core will continue to serve as a center of excellence for the planning and design of investigator-initiated observational studies and behavioral interventions to reduce the risk of HIV infection on the individual, couple, group, and community levels. It will identify previously unrecognized statistical needs and study design improvements at the earliest planning stages in order to generate innovative solutions. The SED Core will meet the biostatistical, epidemiologic, and data management needs of Center-affiliated studies in a centralized and unified manner, consistent with modern principles of conduct of randomized controlled trials for behavioral intervention studies and observational methods for comparative or descriptive, nonexperimental studies. With its tripartite structure, the Core provides an interrelated network of talented specialists who are interdisciplinary and collaborate on all aspects of marshaling evidence: study design and instrumentation, anticipation and avoidance of bias, data management, statistical analysis and weighing of evidence, and interrelation with other disciplines to evaluate evidence and make causal inferences. The Statistics Component increases the likelihood that the randomized trials and observational studies will achieve their scientific goals through the application of good statistical principles and practices that minimize threats to validity. The biostatistical faculty and staff in the Core are highly experienced in collaborating with investigators in keeping studies on target and are pro-active in identifying and seeking resolutions to new statistical problems. The Epidemiology Component sits at the interface of the behavioral and biomedical sciences and thus is uniquely positioned to contribute to the articulation and refinement of research questions, to the selection of appropriate study designs, to the resolution of issues that arise in the field, and to the interpretation of the resulting data. The Data Management Component provides state-of-the-art management of research information, including forms production, ACASI instrumentation, and web-based research products. The integration of these skills and resources into one Core has led to a synergistic interaction of disciplines to identify and develop specific technical methods and products that will enhance the research productivity of the Center and support new and innovative research.